You have survey results, and one of the questions splits cleanly into a few answers that add up to everyone who responded. A pie chart is the chart most people reach for first, and it is also the one most often misused. This article explains how it works, how to build one by hand, and when to choose something else. It is part of our guide to charting survey data, which compares all the common chart types.
Key takeaways
- A pie chart is a circle divided into slices that show how one whole splits into categories, with slice angles proportional to each share.
- To calculate a slice angle, divide the category’s count by the total and multiply by 360 degrees, so each 1% takes 3.6 degrees.
- Use a pie chart only for one whole with two to five categories where at least one slice is clearly larger or smaller than the rest.
- Choose a bar chart instead when there are more than five categories, the slices are similar in size, or the question allows multiple responses.
- Order slices by size starting at 12 o’clock, label them directly, avoid 3D, and state the base so readers know what the whole is.
How do you read a pie chart?
Read a pie chart in three steps. First, check what the whole circle represents: all respondents, all sales, or all answers to one question.
Second, compare slice sizes. A slice that fills a quarter of the circle is 25%, and one that fills half is 50%. Third, read the labels, which should show each category name and its percentage.
The circle is the total, so a pie chart answers one kind of question: how is this whole divided? It does not show change over time or how two groups differ. A typical survey use is asking 1,000 customers how they usually buy from you, then showing online, in store, app and phone as slices.
What does each part of a pie chart mean?
A pie chart has four parts, and it helps to name them.
- Slice (sector): one category. Its area is proportional to its share of the whole.
- Arc: the curved edge of a slice. Longer arcs mean bigger shares.
- Central angle: the slice’s angle at the center. A full circle is 360 degrees.
- Label and legend: the category name and value, ideally on or beside each slice.
How do you calculate pie chart angles?
To calculate the angle of a slice, divide the category’s count by the total, then multiply by 360 degrees. Equivalently, multiply the percentage by 360. Each 1% of the whole takes up 3.6 degrees of the circle.
Worked example: preferred purchase channel
Suppose 1,000 customers answered the question above. Here are the counts, the shares, and the angles.
| Channel | Respondents | Share of total | Angle (share × 360°) |
|---|---|---|---|
| Online | 420 | 420 ÷ 1,000 = 42% | 0.42 × 360 = 151.2° |
| In store | 300 | 300 ÷ 1,000 = 30% | 0.30 × 360 = 108° |
| App | 180 | 180 ÷ 1,000 = 18% | 0.18 × 360 = 64.8° |
| Phone | 100 | 100 ÷ 1,000 = 10% | 0.10 × 360 = 36° |
| Total | 1,000 | 100% | 360° |
Check your work by adding the angles: 151.2 + 108 + 64.8 + 36 = 360. If the total is off, a count or a percentage is wrong. You can also work backward. A slice with a 90 degree angle is 90 ÷ 360 = 25% of the whole.
When should you use a pie chart?
Use a pie chart when all of the following are true:
- You are showing parts of one whole, and the parts add up to 100%.
- There are two to five categories.
- The point is a rough comparison, such as “about half” or “a small minority”, rather than exact values.
- At least one slice is clearly larger or smaller than the others.
Pie charts suit a single-choice question with a few answers, such as preferred channel or yes, no and unsure. The eye reads simple fractions like a quarter or a half quickly.
When is a bar chart better than a pie chart?
A bar chart is better whenever the exact comparison matters. People judge length along a common baseline more accurately than they judge angle and area, so close values that are hard to tell apart in a pie are obvious in a bar chart. We cover this in detail in our guide to bar charts.
| Situation | Better choice |
|---|---|
| Parts of a whole, 2 to 5 categories | Pie chart |
| More than 5 categories | Bar chart |
| Slices of similar size (for example 24%, 26%, 25%, 25%) | Bar chart |
| Multiple-response questions that exceed 100% | Bar chart |
| Comparing the same breakdown across several groups or waves | Stacked bar chart |
| A headline total shown alongside the split | Donut chart |
If you cannot tell which slice is larger without reading the labels, switch to bars.
What is the difference between a pie chart and a donut chart?
A donut chart is a pie chart with the center removed. The data and the logic are the same: slices show shares of a whole. Our guide to the donut chart goes deeper, but the short comparison is below.
| Pie chart | Donut chart | |
|---|---|---|
| Shows | Parts of a whole | Parts of a whole |
| Reads by | Angle and area | Arc length |
| Center | Filled | Empty, can hold a total or key figure |
| Best for | Quick read of the biggest share | Pairing the split with a headline number |
A donut is slightly harder to read because the eye has less area to compare. Pick it when the hole earns its place, for instance to show “1,000 respondents” in the middle.
How do you design a pie chart people can read?
Good pie charts follow a few simple rules.
- Keep slices to five or fewer. Group the smallest categories into “Other”, and say what is in it.
- Order slices by size. Start the largest at 12 o’clock and go clockwise from big to small. The exception is a naturally ordered scale, such as strongly disagree to strongly agree, where you keep the scale order.
- Label slices directly. Put the category name and percentage on or beside each slice so nobody has to match colors to a legend.
- Use distinct colors, and no more than needed. Pick colors that stay distinguishable for color-blind readers, or use one color for the focus slice and neutral grays for the rest.
- Keep it flat. Never use a 3D pie chart. Tilting the circle makes the front slices look bigger than the back ones, which distorts the data.
- Make the total clear. State the base, such as “n = 1,000 respondents”, so readers know what the whole is.
What are the common mistakes with pie charts?
- Too many slices. Ten thin wedges cannot be compared. If you need them all, use a bar chart.
- Percentages that do not total 100%. Rounding can leave you at 99% or 101%. Note that in a footnote, and never adjust numbers silently.
- Exploded slices. Pulling slices out of the circle adds clutter without adding meaning.
- Using one pie for multiple-response data. If respondents can pick more than one answer, the total exceeds 100% and there is no single whole to divide.
- Comparing several pies side by side. Judging slice sizes across circles is hard. Use a stacked bar chart to compare groups.
How do you make a pie chart in practice?
Tabulate the question first so you have counts and percentages, then chart the result. In Halo Reports you can run weighted crosstabs with significance testing and turn the results into charts and interactive report pages, so the chart you share is based on the same numbers as your tables. Spreadsheet tools work too, as long as you have the percentages right and follow the design rules above. To see which splits have shifted since the last wave, mTab Pulse monitors trackers and studies and surfaces meaningful movement.
Before you build your next pie chart, count the categories and look at the slice sizes. If you have more than five categories, or the shares are close together, make it a bar chart instead. If you do use a pie, order the slices, label them directly, and state the base. If the result is headed for senior readers, an executive brief is a one-page way to say what changed, why it matters and what to do.